Program/erase method for P-channel charge trapping memory device

Abstract

A method of operating a memory device is disclosed, wherein the memory device includes an n-type substrate and a plurality of memory cells formed thereon, each memory cell corresponding to a word line, a first bit line, and second bit line, and including a first bit portion and a second bit portion each for storing one bit of information. The method includes resetting a selected memory cell by applying a first negative bias to the word line of the selected memory cell and applying a ground bias to the first and second bit lines, and programming the first bit portion of the selected memory cell by applying a first positive bias to the word line of the selected memory cell, applying a second negative bias to the first bit line of the selected memory cell, and applying a ground bias to the second bit line of the selected memory cell.

1. A method of operating a memory device, wherein the memory device includes an n-type substrate and a plurality of memory cells formed thereon, each memory cell including a control gate, a source region, a drain region, a channel region defined between the source and drain regions, a trapping layer provided above the channel region, a first insulating layer provided between the trapping layer and the channel region, and a second insulating layer provided between the trapping layer and the control gate, wherein the control gate corresponds to a word line, the source region corresponds to a first bit line, and the drain region corresponds to a second bit line, and wherein each memory cell includes a first bit portion and a second bit portion each for storing one bit of information, the method comprising:
 resetting a selected memory cell, including
 applying a first negative bias to the word line of the selected memory cell, and 
 applying a ground bias to both the first bit line and the second bit line; and 
 
 programming the first bit portion of the selected memory cell, including
 applying a first positive bias to the word line of the selected memory cell, 
 applying a second negative bias to the first bit line of the selected memory cell, and 
 applying a ground bias to the second bit line of the selected memory cell. 
 
 
   
   
     2. The method of  claim 1 , further including providing the first bit portion of the memory cell as a part of the trapping layer adjacent to the corresponding first bit line, and providing a second bit portion as a part of the trapping layer adjacent to the corresponding second bit line. 
   
   
     3. The method of  claim 1 , further including resetting the selected memory cell by first and second electron tunneling processes, wherein in the first tunneling process, electrons tunnel from the control gate of the selected memory cell, through the first insulating layer of the selected memory cell, into the trapping layer of the selected memory cell, and in the second tunneling process, electrons tunnel out of the trapping layer of the selected memory cell, through the second insulating layer of the selected memory cell, into the channel region of the selected memory cell. 
   
   
     4. The method of  claim 3 , further including reaching a dynamic balance reached between the first and second electron tunneling processes when the selected memory cell is reset. 
   
   
     5. The method of  claim 4 , further comprising erasing the selected memory cell, including
 applying a third negative bias to the word line of the selected memory cell, wherein the second negative bias has a predetermined high value, and 
 applying the ground bias to both the first bit line and the second bit line of the selected memory cell. 
 
   
   
     6. The method of  claim 5 , further including applying the third negative bias as approximately equal to the first negative bias. 
   
   
     7. The method of  claim 6 , further including reaching the dynamic balance between the first and second electron tunneling processes when the selected memory cell is erased. 
   
   
     8. The method of  claim 1 , wherein programming the first bit of the selected memory cell causes tunneling of electrons into a portion of the trapping layer adjacent the first bit line of the selected memory cell. 
   
   
     9. The method of  claim 1 , further comprising programming the second bit of the selected memory cell, including
 applying a second positive bias to the word line of the selected memory cell, 
 applying a third negative bias to the second bit line of the selected memory cell, and 
 applying the ground bias to the first bit line of the selected memory cell. 
 
   
   
     10. The method of  claim 1 , further comprising reading the first bit portion of the selected memory cell, including
 applying a second positive bias to the word line of the selected memory cell; 
 applying a ground bias to the first bit line of the selected memory cell; and 
 applying a third negative bias to the second bit line of the selected memory cell. 
 
   
   
     11. The method of  claim 10 , further including applying the second positive bias as smaller than a threshold voltage of the programmed first bit portion of the memory cell and greater than a threshold voltage of the selected memory before the first bit portion or the second bit portion thereof is programmed. 
   
   
     12. An operation method of a memory device, wherein the memory device includes a semiconductor substrate, a plurality of discontinuous bit lines formed in the substrate, each discontinuous bit line including a plurality of diffusion regions spaced apart from each other, and a plurality of word lines, each of which corresponds to a gate that comprises a material with a high work function and formed over the substrate, wherein the plurality of word lines and the plurality of discontinuous bit lines define a plurality of memory cells, each memory cell corresponding to one word line and two consecutive ones of the plurality of diffusion regions of a discontinuous bit line, and wherein each discontinuous bit line has a first end and a second end, the method comprising:
 selecting a memory cell, including
 applying a turn-on voltage to all of the plurality of word lines except the word line of the selected memory cell, and 
 applying a ground bias to both the first end and the second end of all of the plurality of discontinuous bit lines except the discontinuous bit line of the selected memory cell; and 
 
 operating the selected memory cell. 
 
   
   
     13. The method of  claim 12 , further including:
 providing the semiconductor substrate with an n-type conductivity; 
 providing the plurality of diffusion regions with a p-type conductivity; and 
 applying the turn-on voltage as a negative voltage. 
 
   
   
     14. The method of  claim 12 , wherein operating the selected memory cell comprises resetting the selected memory cell, including
 applying a first negative bias to the word line of the selected memory cell, and 
 applying the ground bias to both the first end and the second end of the discontinuous bit line of the selected memory cell. 
 
   
   
     15. The method of  claim 14 , further including providing the word line of each memory cell as a layer of control gate, and providing each memory cell as including an n-type substrate, a channel region defined between the corresponding two consecutive diffusion regions, a trapping layer provided above the channel region, a first insulating layer provided between the trapping layer and the channel region, and a second insulating layer provided between the trapping layer and the control gate. 
   
   
     16. The method of  claim 15 , further including resetting the selected memory cell by first and second electron tunneling processes, wherein in the first tunneling process, electrons tunnel from the control gate of the selected memory cell, through the first insulating layer of the selected memory cell, into the trapping layer of the selected memory cell, and in the second tunneling process, electrons tunnel out of the trapping layer of the selected memory cell, through the second insulating layer of the selected memory cell, into the channel region of the selected memory cell. 
   
   
     17. The method of  claim 16 , further including reaching a dynamic balance between the first and second electron tunneling processes when the selected memory cell is reset. 
   
   
     18. The method of  claim 17 , wherein operating the selected memory cell further comprises erasing the selected memory cell, including
 applying a second negative bias to the word line of the selected memory cell, wherein the second negative bias has a high value, and 
 applying the ground bias to both the first bit line and the second bit line of the selected memory cell. 
 
   
   
     19. The method of  claim 18 , further including applying the second negative bias as approximately equal to the first negative bias. 
   
   
     20. The method of  claim 19 , further including reaching the dynamic balance between the first and second electron tunneling processes when the selected memory cell is erased. 
   
   
     21. The method of  claim 12 , wherein each memory cell includes a first bit portion and a second bit portion, and operating the selected memory cell comprises programming the first bit portion of the selected memory cell, including
 applying a positive bias to the word line of the selected memory cell, 
 applying a negative bias to the first end of the discontinuous bit line of the selected memory cell, and 
 applying the ground bias to the second end of the discontinuous bit line of the selected memory cell. 
 
   
   
     22. The method of  claim 12 , wherein each memory cell includes a first bit portion and a second bit portion, and operating the selected memory cell comprises reading the first bit portion of the selected memory cell, including
 applying a positive bias to the word line of the selected memory cell, 
 applying a ground bias to the first end of the discontinuous bit line of the selected memory cell, and 
 applying a negative bias to the second end of the discontinuous bit line of the selected memory cell. 
 
   
   
     23. The method of  claim 22 , further including applying the positive bias as smaller than a threshold voltage of the first bit portion of the memory cell when the first bit portion of the memory cell is programmed and greater than a threshold voltage of the selected memory before when the first bit portion or the second bit portion of the memory cell is not programmed.